Planographic repellent solution and method of preparing the same



Patented July 18, 1950 PLAN OGRAPHIC REPELLENT SOLUTION AND METHOD OFPREPARING THE SAME Charles H. Van Dusen, Jr., Willoughby, Ohio, assignorto Addressograph-Multigraph Corporation, Wilmington, DeL, a corporationof Delaware No Drawing. Application April 5, 1946,

Serial No. 659,870

4 Claims. (Cl. 101-1492) This invention relates to a so-called repellentsolution for use upon planographic printing plates including parchmentor like cellulose base and metal planographic printing plates, and to amethod of making the said solution. The general uses and functions orpurposes of such solutions are well-known in the art and are disclosed,for example, in United States Letters Patents Nos. 1,977,646, 2,003,268and 2,393,875, to which reference may be had for a disclosure of thegeneral nature and purposes of such solutions. In general it may besaid, however, that such solutions are of the two types, namely, thosewhich are applied directly to the plates as etching solutions at thestart of a planographic printing operation to render the non-printingareas of the plate repellent to greasy or fatty acid-containingplanographic printing inks and those which are employed for the samepurpose as so-called fountain repellent solutions upon rotary offsetplanographic duplicating machines. In the latter instance the repellentfountain solution in addition to serving as a dampening or repellentsolution, per se, keeps the planographic printing plate moist andprevents it from scumming up when the machine is stopped temporarilyduring the printing of long runs or editions. The repellent solution ofthe present invention is particularly adapted for use as a fountainsolution in rotary offset planographie duplicating apparatus.

It is customary to include in such planographic repellent solutions ahygroscopic agent which has commonly been glycerine and it has beencustomary to put such solutions in concentrated form in bottles or likecontainers and dilute them prior to use. This, of course, necessitatesthe additional diluting operation and usually requires the use ofdistilled water since ordinary tap water is generally not suitable forthe purpose of diluting such repellent solutions. 1 A number ofdifilculties have been encountered heretofore in'attempts to useplanographic repellent solutions of low water content and among thesehave been the glazing of the ink rolls embodied in rotary oii'setplanographic duplicating apparatus. While I am not entirely certain asto the physical orgchemical phenomena which cause this'objectionableglazing of the ink rolls I believe that it is due to the tendency ofsuch lowz water content repellent solutions to form an emulsion of theoil-in-water type with the greasy orfatty acid inks employed in therotary offset planographic duplicating apparatus with which suchrepellent solutions are used as fountain solutions and that the thusformed oil-in-water type emulsion, in some manner not clearlyunderstood, causes the aforesaid objectionable glazing of the ink rolls.In any event, the glazed surface thus formed on the ink rolls repels theink and thus eventually prevents proper inking of the ink rolls, themaster planographic printing plate, the blanket and the copy. Moreover,such glazed surfaces are extremely hard and difficult to remove, beingresistant to the action of common solvents and necessitating an abradingoperation to effect their removal from the ink rolls.

I have found that the aforesaid glazing action of the repellent solutioncommences when the water content of the repellent fountain solution isabout eighty per cent, by weight, and increases progressively with adecrease in the water content of the solution.

It is well known that when parchment and like cellulose base or otherwater-absorbent and water-expansible planographic printing plates aremoistened with glycerine-water repellent solutions the water content ofthe solutions causes such plates to stretch or expand with resultingdistortion of the image on the master plate and on the copies reproducedtherefrom. Such stretching or expansion are directly related to andincrease with the water content of a gylcerine-water repellent solution.Hence it will be seen that the stretching or expansion of parchment orlike water-absorbent and waterexpansible planographic printing platesmay be reduced by reducing the water content of such glycerine-waterrepellent solutions.

However. in the practice of the present invention I have found that ifthe water content of a glycerine-water repellent solution is reducedwith a view toward, and for the purpose of, prevent.- ing stretching orexpansion of water-absorbent and water-expansible planographio .printingplates, such as parchment plates, with resulting proportionate increasein the glycerine content of the solution, the resulting solution tendsto form the aforesaid objectionable oil-cin-water type of emulsion withconsequent glazin of the ink rolls in the rotary offset planographicprinting presses with which such planographic printing plates are used,as explained hereinbefore.

It will thus be seen that for the purpose of minimizing the stretchingor expansion of waterabsorbent and water-expansible planographicprinting plates moistened thereby it is desirable to reduce the watercontent of a glycerine-water repellent solution so that the same berelatively low in relation to the glycerine content, while at the sametime, for the purpose of preventing the formation of the aforesaidobjectionable oilin-water type emulsion with greasy or fattyacidcontaining planographic printing inks it is desirable that the watercontent of such glycerinewater repellent solutions be relatively high inrelation to the glycerine content.

Prior glycerine-water repellent solutions have usually been somewhatacid in nature and, as pointed out hereinbefore, cause objectionablestretching or expansion of water-absorbent and water-expanslbleplanographic printing plates moistened thereby including parchmentplates and the like. However, in the practice of the present invention Ihave found that the water content of a glycerine-water repellentsolution may be maintained relatively high in relation to the glycerinecontent, and the glycerine content of the solution correspondingly low,without causing objectionable stretching or expansion of thewater-absorbent and water-expansible planograph printing platesmoistened by the solution if the solution is rendered somewhat more acidand its pH established and controlled in a manner which will bedescribed presently. So to do is a primary object of the presentinvention.

Related objects of the present invention are to provide a new andimproved low water content glycerine-water repellent solution which whenused as a fountain solution in conjunction with water-absorbent andwater-expansible planographic printing plates, including parchmentplates, prevents the objectionable spreading or stretching of suchplates incidental to the use of prior glycerine-water planographicrepellent fountain solutions. a

Another object of the present invention is to provide a novel method ofmaking the new repellent solution and of assuring that the same has thedesired controlled pH value.

Thus I have found that if the water content of the new glycerine-waterrepellent solution is maintained at not substantially more than eightyper cent of the entire composition or complete solution, and if theglycerine content of the solution is maintained at not substantiallyless than twenty per cent nor substantially more than eighty per cent ofthe entire composition or complete solution, by weight, and if the pH ofthe solution is maintained at not substantially more than 4.0 and notsubstantially less than 3.0, a repellent fountain solution is affordedwhich materially reduces the expansion or stretching of parchment andlike water-absorbent and waterexpansible planographic printing platesmoistened thereby while, at the same time, the new repellent fountainsolution materially reduces the tendency of such glycerine-waterfountain repellent solutions to form an emulsion of the oil-in-watertype with fatty or greasy lithographic inks and hence correspondinglyreduces the tendency of such solutions to cause glazing of the ink rollsin rotary planographic duplicating presses with which such repellentfountain solutions are used.

Moreover, I have found that if the glycerine content of the newglycerine-water repellent fountain solution is established at aboutsixty per cent, .by weight, of the entire composition or completesolution the rate of expansion of parchment and like water-absorbent andwater-expansible planographic printing plates moistened thereby ismaterially less than the rate of expansion in similar plates moistenedwith prior low glycerine content and high water content repellentfountain solutions and that the total expansion or stretch in similarplates moistened with the prior low glycerine content high water contentrepellent fountain solutions.

I have found further that if the glycerine content in the newglycerine-repellent fountain solution is increased to eighty per cent orabove, by weight, as may be done without causing glazing of the inkrolls, expansion or stretch of parchment and like plates moistenedthereby is entirely eliminated.

Moreover, I have found that when the water content of the newglycerine-water repellent fountain solution is decreased to provide arelatively high glycerine content in the new repellent fountain solutionthe tendency of the repellent fountain solution to form an oil-in-watertype emulsion with fatty or greasy lithographic inks and resultingglazing of the ink rolls may be materially reduced by the addition of apreselected quantity of formaldehyde or other watersoluble aldehyde tothe solution. When thus incorporated in the new repellent solution theformaldehyde or other water-soluble aldehyde makes it possible toutilize a relatively high glycerine content in the new repellentfountain solutionwithout causing glazing of the ink rolls in the presseswith which the new repellent solution is used while, at the same time,the reduction of the pH of the solution to a pH of not substantially inexcess of 4.0 makes it possible to employ a relatively high watercontent in the new repellent solution while materially reducing both therate of expansion and the total expansion or stretch of parchment andlike waterabsorbent and water-expansible planographic printing platesmoistened thereby.

A suitable formula which may be employed in preparing the newplanographic repellent fountain solution is shown in the followingexample in which all parts are in terms of per cent, by weight:

" Example No. 1

Per cent by weight Formaldehyde (37 per cent solution in water)(Formalin) 0.5

Mono-ammonium dihydrogen phosphate Plus 10 cc. of phosphoric acid, HsPOr(85 per cent) in 4000 grams of the complete solution.

It will be noted that the glycerine content of the glycerine-waterrepellent fountain solution set forth in the foregoing Example No. 1 isapproximately sixty per cent by weight of the entire composition orcomplete solution.

In preparing the new repellent solution having the composition set forthin the foregoing Example No. 1, the mono-ammonium dihydrogen phosphateand the aqueous formaldehyde solution are first preferably thoroughlymixed together, and the glycerine and water are then added to andthoroughly mixed with the solution thus formed. By thus mixing thevarious ingredients of the new repellent solutions the pH of thesolutiondrops in the presence of the formaldehyde and comes to anequilibrium in a signiflcantly shorter time than would otherwise berequired to bring the pH of the solution to equilibrium if theformaldehyde were added last. "The quantity of phosphoric acid indicatedin the foregoing Example No. 1 may then be added to the solution so asto reduce and adjust the pH of the thus completed and resulting solutionto a value of approximately 3.0.

In the new repellent solution prepared as in the foregoing Example No. 1the mono-ammonium phosphate serves as a buffer to maintain the pH of thesolution at a value of approximately 3.0, to which pH the solution isreduced by the addition of phosphoric acid.

The formaldehyde component of the new repellent solution, prepared as inthe foregoing Example No. 1, serves to prevent the new repellentsolution from forming an oil-in-water type of emulsion with fatty orgreasy lithographic inks and consequent glazing of the ink rolls of theplanographic printing presses with which the new repellent solution maybe used. At the same time the formaldehyde component of the solutionprevents the formation of fungus mold growth in the solution.

In the practice of the present invention I have found that the quantityof formaldehyde incorporated into the solution should be within acritical range of not substantially less than 0.1 per cent norsubstantially more than 2.0 per cent of the complete composition, byweight, the formaldehyde being calculated as HCHO, or equivalent amountsof other water-soluble aldehydes. The quantity of formaldehyde, or otherwater-soluble aldehyde, employed in the new repellent solution may bevaried somewhat between the critical limits specified depending, inpart, upon the glycerine content of the solution, being greater for ahigher glycerine content and less for a lower gb'cerine content.

In place of all or a part of the formaldehyde specified in the foregoingExample No. l,-I may employ equivalent amounts of other water-solublealdehydes in the new repellent solution, with correspondingly good andsimilar results, and among such other water-soluble aldehydes which maybe used are furfuraldehyde, acetaldehyde and glyoxal.

Thus, a suitable formula which may be employed in making the newrepellent solution, utilizing furfuraldehyde in place of formaldehyde,is illustrated in the following example in which all parts indicated arein terms of per cent by weight:

Example No. 2

Per cent by weight 0.5

Furfuraldehyde (Furfural) Mono-ammonium di-hydrogen phosphate Plussufficient phosphoric acid (HaPOt) to reduce the pH of the solution tobetween 3.0 and 4.0.

A suitable formula which may be followed in preparing the new repellentfountain solution and which employs a percentage of glycerine whichconstitutes the lower limit of the critical range hereinbeforespecified, namely, twenty per cent of glycerine, by weight, is shown inthe following example in which all parts indicated are in terms of percent, by weight:

Example No. 3

Per cent by weight Formaldehyde (37 per cent solution in water)(Formalin) 0.5

Mono-ammonium dihydrogen phosphate (NHOHMPOQ 2.0 Glycerine 20.0 Water-3"; 77.5

Plus 2.8 c. c. of phosphoric acid (HsPO-i) per cent) in 4000 grams ofthe complete solution.

A suitable formula which may be followed in pireparing the new repellentsolution with a glycerine content of eighty per cent, by weight, of theentire composition or complete solution. and which is the'upper limit ofthe aforesaid critical range of the glycerine content of the newrepellent fountairr solution, is shown in the following example in whichall parts indicated are in terms of per cent by weight:

Example No. 4

n Per cent by weight Formaldehyde (37 per cent solution in water)(Formalin) 0.5

Mono-ammonium dihydrogen phosphate (NHA) H2(P04) 2.0 Glycerine 80.0Water 17.5

Plus 8.9 c. c. of phosphoric acid (HJPOO (85 per cent) in 4000 grams of.the com plete solution.

plates with which it is used but appears to remain upon the surfacethereof.

By the terms complete solution and complete repellent solution, asusedhereinafter in the claims, in reference to the percentages in whichthe several ingredients or components of the solution are employed inmaking the same, is meant the solution as it exists and is composedprior to the addition of the phosphoric acid (H2204) thereto.

It will thus be seen from the foregoing .de-

scription that the present invention provides a a new and improved lowwater content planographic dampening or so-called repellent fountainsolution, and a novel method of preparing the same, and that the presentinvention thus has the desirable advantages and characteristics, andaccomplishes its intended objects, including those hereinbefore pointedout and others which are inherent in the invention.

1 I claim: 1. A planographic repellent composition comprising a solutionor water, glycerine, monoammonium dihydrogen phosphate and formaldehyde,the said water component of the said planographic repellent compositionconstituting not substantially more than eighty per cent 01' thecomplete repellent composition and the aid glycerine component of thesaid repellent composition constituting not substantially less thantwenty per cent nor substantially more than eighty per cent oi thecomplete repellent composition, by weight, the said formaldehydecomponent of the said repellent composition constituting notsubstantiallyless than 0.1 per cent nor substantially more than 2.0 percent of the complete repellent composition, by weight, and beingcalculated as 100 per cent formaldehyde, and the said repellentcomposition having a pH oi not substantially more than 4.0 norsubstantially less than 3.0.

2. A planographic repellent composition comprising a solution 01 water,glycerine, monoammonium dihydrogen phosphate (NHOH: (P04) and awater-soluble aldehyde, the said water plete repellent composition, byweight, the said water-soluble aldehyde component of the said repellentcomposition constituting not substantially less than 0.1 per cent norsubstantially more than 2.0 per cent 0! the complete repellentcomposition, by weight, and being calculated as 100 per centwater-soluble aldehyde, and the said repellent composition having a pHoi. not substantially more than 4.0 nor substantially less than 3.0.

3. A planographic repellent composition as deiined in claim 1 whichcontains, in addition to the ingredients therein specified, a minorproportion of phosphoric acid (HaPOr).

4. A planographic repellent composition as defined in claim 2 whichcontains, in addition to the ingredients therein specified, a minorproportion of phosphoric acid (HaPOO CHARLES H. VAN DUSEN, Ja.

REFERENCES crrnn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,976,039 Rowell Oct. 9, 19342,003,286 Wescott May 28, 1935 2,240,486 Beckley May 6, 1941 2,374,070Barensileld Apr. 17, 1945 2,393,875 Van Dusen Jan. 29, 1946 OTHERREFERENCES The Lithographers Manual (1940), pages 209 and 216, WaltwinPublishing Co., 1776 Broadway, New York city. (Copy in Div. 17.)

2. A PLANOGRAPHIC REPELLENT COMPOSITION COMPRISING A SOLUTION OF WATER,GLYCERINE, MONOAMMONIUM DIHYDROGEN PHOSPHATE